1. Field of the Invention
The present invention relates to an ink jet recording apparatus, and in particular, to an electrostatic ink jet recording apparatus that carries out recording using the effects of electric fields to deposit charged toner in ink on a recording medium.
2. Description of the Prior Art
As described in the PCT International Publication Number WO 93/11866, conventional electrostatic ink jet apparatuses have a recording head body with ejection electrodes for ejecting ink and an opposite electrode disposed opposite to the recording head body.
As shown in FIG. 1, a plurality of ejection electrodes 52 are provided at the end of a recording head body 50 so as to protrude therefrom. An opposite electrode 53 is disposed on the extension of the ejection electrodes 52 via a recording medium 58. The plurality of ejection electrodes 52 are arranged in parallel at an interval depending on the recording resolution are immersed in ink. The ink comprises an ink liquid containing charged particulate material (charged toner) and can reach the end of the ejection electrodes due to surface tension. Compared to the plurality of ejection electrodes 52, the opposite electrode 53 comprises a common integral electrode and is grounded.
When a high voltage pulse is applied to any ejection electrode 52, there will be an electric potential difference between the end of the ejection electrode 52 and the opposite electrode 53. Electric fields (electric force lines 63) formed depending on the potential difference cause the ink to be ejected from the end of the ejection electrode 52 toward the opposite electrode 53. The ejected ink deposits on the recording medium 58 disposed in front of the opposite electrode 53 for recording. Compared to the ejection electrode 52, to which the high voltage pulse has been applied, the potential around the ink deposition location on the opposite electrode 53 is uniform. The ink thus flies in the direction in which the distance between the ejection electrode 52 and the opposite electrode 53 is shortest due to the strength of the corresponding electric field, that is, a direction A, and the ink deposits at a location B.
According to this conventional example, however, there is only a small difference in magnitude between the electric field indicated at A and peripheral electric fields (for example, the one indicated at C), so the magnitude of the electric field C may become larger than that of the electric field A if, for example, the surface of the recording paper is rough or dust sticks to the paper. In such a case, the ink, flying along the electric field C, may deposit at a location D, and this deviation of the recording location may cause image quality to be degraded.